Recent studies from this laboratory have established that Enterobacteria on the vaginal vestibule determine recurrence of bacteriuria in the adult female, while women immune to urinary infections resist colonization of their introital mucosa. The major aim of this renewal application is to establish the biologic basis for this difference in introital bacteriology between normal women and those susceptible to recurrent bacteriuria. To determine the role of vaginal pH and vaginal antibody, women with recurrent bacteriuria will be followed at frequent intervals to measure (1) the bacterial flora of the vaginal vestibule, urethral and midstream cultures; (2) surface pH of the introital mucosa; (3) glygogen and a- amylase content of the vaginal fluid. Using the vaginal model of the adult rabbit, the fate of bacterial inoculation of the vagina will be studied in both the normal and oophorectomized rabbit.